PY3DX - Paulo Ricardo Toledo Rua Liberal, 1001 - Bairro Ipanema Zip: 91920-680 Porto Alegre - RS - Brazil Phone ++ 55 (51) 242-8357 Phone:++ 55 (51) 320-3551 E-mail: toledo@pucrs.br Home-page: www.qsl.net/py3paz